JP2015061091A - Atomic resonant transition device, atomic oscillator, electronic apparatus, and mobile body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an atomic resonant transition device and an atomic oscillator that improve long-term frequency stability by preventing or suppressing a change with time in the amount of magnetization of a shield part by a magnetic field from an exciting coil, and provide a reliable electronic apparatus and mobile body equipped with the atomic resonant transition device.SOLUTION: An atomic oscillator 1 of the present invention includes: an alkali metal; an exciting coil (coil 35) for applying a DC magnetic field to the alkali metal; a shield part shielding the alkali metal from an external magnetic field; a power supply 4 capable of simultaneously generating a direct current and an alternating current attenuated with time; and a demagnetizing coil (coil 35) supplied with the direct current and the alternating current to generate a demagnetizing field, in which a DC magnetic field component and an AC magnetic field component attenuated with time are superimposed together, for demagnetizing the shield part.

Description

  The present invention relates to an atomic resonance transition device, an atomic oscillator, an electronic device, and a moving object.

An atomic oscillator is known as an oscillator having long-term highly accurate oscillation characteristics. In general, the operating principles of atomic oscillators are broadly divided into methods that use the double resonance phenomenon of light and microwaves, and methods that use the quantum interference effect (CPT: Coherent Population Trapping) of two types of light with different wavelengths. However, any type of atomic oscillator oscillates based on the energy transition of alkali metal atoms such as rubidium and cesium.
As such an atomic oscillator, for example, as disclosed in Patent Document 1, an excitation coil that applies a magnetic field to a transition part that causes resonance transition of an alkali metal, and a magnetic shield that shields the excitation coil and the transition part from an external magnetic field, Are known.

  The atomic oscillator according to Patent Document 1 normally operates in a normal mode in which an excitation current is supplied to the excitation coil. However, when the frequency accuracy is reduced due to the magnetization of the magnetic shield, the atomic oscillator is alternately switched. Then, the mode is selectively switched to a degaussing mode that supplies an alternating current that gradually decreases. Then, after the demagnetization process of the magnetic shield is performed in the demagnetization mode, the mode is switched again to the normal mode.

  However, in the atomic oscillator according to Patent Document 1, since the demagnetization process is performed so that the magnetization amount of the magnetic shield becomes zero in the demagnetization mode, the magnetic shield whose magnetization amount becomes zero in the demagnetization mode is the normal mode. After the transition, it takes a long time from several hours to several months until the magnetization by the magnetic field from the exciting coil in the normal mode is stabilized. For this reason, the atomic oscillator according to Patent Document 1 has a problem in that the fluctuation in the amount of magnetization of the magnetic shield during that period affects the long-term stability of the frequency and the long-term stability of the frequency is lowered.

JP 61-131621 A

  An object of the present invention is to provide an atomic resonance transition device and an atomic oscillator that can prevent or suppress a change in the amount of magnetization of a shielding portion over time due to a magnetic field from an exciting coil and improve long-term frequency stability. Another object of the present invention is to provide a highly reliable electronic apparatus and moving body including the atomic resonance transition device.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Application Example 1]
The atomic resonance transition device of the present invention comprises a metal atom,
An exciting coil for applying a DC magnetic field to the metal atoms;
A shielding part having magnetic shielding properties;
A power source capable of simultaneously generating a direct current and an alternating current that decays over time;
A degaussing coil for generating a demagnetizing magnetic field in which the direct current and the alternating current are supplied and a direct current magnetic field component and an alternating magnetic field component that decays with time are superimposed;
It is characterized by having.

  According to such an atomic resonance transition device, the shield part is demagnetized by a demagnetizing magnetic field from the degaussing coil while leaving a slight amount of magnetization similar to that magnetized by the DC magnetic field from the exciting coil. be able to. Therefore, when a DC magnetic field is generated from the exciting coil after demagnetizing the shielding part, it is possible to prevent or suppress changes in the amount of magnetization of the shielding part over time due to the DC magnetic field from the exciting coil. As a result, the strength of the magnetic field applied to the metal atoms can be stabilized, and the long-term stability of the frequency can be improved.

[Application Example 2]
In the atomic resonance transition device of the present invention, the power supply can output a current obtained by superimposing the direct current and the alternating current,
Preferably, the demagnetizing coil is supplied with the superimposed current from the power source to generate the demagnetizing magnetic field.
As a result, a demagnetizing magnetic field in which a DC magnetic field component and an AC magnetic field component that decays with time can be generated from a degaussing coil constituted by one coil.

[Application Example 3]
The atomic resonance transition device of the present invention includes a magnetic field control unit for controlling the power supply,
The magnetic field control unit is preferably switchable between a degaussing mode for supplying the superimposed current to the degaussing coil and a normal mode for supplying the direct current to the exciting coil.
Thereby, the shielding part can be demagnetized at an arbitrary timing.

[Application Example 4]
In the atomic resonance transition device of the present invention, it is preferable that the exciting coil also serves as the demagnetizing coil.
Thereby, the number of parts can be reduced, and the atomic resonance transition device can be reduced in size and cost.

[Application Example 5]
In the atomic resonance transition device of the present invention, the power source can output the direct current and the alternating current independently,
The degaussing coil includes an alternating magnetic field coil that generates the alternating magnetic field component when the alternating current is supplied from the power source, and a direct current magnetic field coil that generates the direct magnetic field component when the direct current is supplied from the power source. It is preferable to have.
Thereby, the freedom degree of design of an atomic resonance transition apparatus can be raised.

[Application Example 6]
The atomic resonance transition device of the present invention includes a magnetic field control unit for controlling the power supply,
The magnetic field control unit can switch between a demagnetization mode for supplying the DC current to the DC magnetic field coil and supplying the alternating current to the AC magnetic field coil, and a normal mode for supplying the DC current to the excitation coil. It is preferable that
Thereby, the shielding part can be demagnetized at an arbitrary timing.

[Application Example 7]
In the atomic resonance transition device of the present invention, it is preferable that the excitation coil also serves as the DC magnetic field coil.
Thereby, the number of parts can be reduced, and the atomic resonance transition device can be reduced in size and cost.

[Application Example 8]
In the atomic resonance transition device of the present invention, the shielding part includes an inner shielding part and an outer shielding part arranged inside and outside,
The DC magnetic field coil is disposed between the metal atom and the inner shielding portion,
The AC magnetic field coil is preferably disposed between the inner shielding portion and the outer shielding portion.
Thereby, when a package is comprised by the inner side shielding part, the size reduction of the package can be achieved. Further, when the package is an airtight package, it is easy to keep the degree of vacuum in the package high by downsizing. Further, both the inner shielding part and the outer shielding part can be efficiently demagnetized.

[Application Example 9]
The atomic oscillator of the present invention includes the atomic resonance transition apparatus of the present invention.
According to such an atomic oscillator, it is possible to prevent or suppress a change in the amount of magnetization of the shielding portion with time due to the magnetic field from the exciting coil, and improve the long-term stability of the frequency.
[Application Example 10]
The electronic device of the present invention includes the atomic resonance transition device of the present invention.
Thereby, an electronic device having excellent reliability can be provided.
[Application Example 11]
The moving body of the present invention includes the atomic resonance transition apparatus of the present invention.
Thereby, the moving body excellent in reliability can be provided.

1 is a perspective view showing an atomic oscillator according to a first embodiment of the present invention. It is a schematic diagram which shows schematic structure of the atomic oscillator shown in FIG. It is a figure for demonstrating the energy state of the alkali metal in the gas cell with which the atomic oscillator shown in FIG. 1 was equipped. 2 is a graph showing a relationship between a frequency difference between two lights from a light emitting unit and a detection intensity at the light detecting unit for the light emitting unit and the light detecting unit provided in the atomic oscillator shown in FIG. 1. It is a longitudinal cross-sectional view of the atomic oscillator shown in FIG. It is sectional drawing which expands and shows a part of FIG. It is a block diagram for demonstrating the magnetic field control part shown in FIG. (A) is a graph showing the change over time of the current flowing through the exciting coil in the conventional demagnetization mode, and (b) is a diagram of the shield part when the demagnetization mode using the current shown in (a) is shifted to the normal mode. It is a graph which shows a time-dependent change of the magnetization amount. FIG. 7A is a graph showing a change over time of the current flowing in the excitation coil (demagnetization coil) from the power source shown in FIG. 7 in the demagnetization mode, and FIG. It is a graph which shows a time-dependent change of the magnetization amount of the shield part when transfering to. It is a graph which shows the modification of the time-dependent change of the electric current which flows into an exciting coil (degaussing coil) at the time of a degaussing mode from the power supply shown in FIG. It is sectional drawing which expands and shows a part of atomic oscillator which concerns on 2nd Embodiment of this invention. It is a block diagram for demonstrating the magnetic field control part of the atomic oscillator shown in FIG. It is a graph which shows the time-dependent change of the electric current which flows into a degaussing coil at the time of a degaussing mode from the power supply shown in FIG. It is a system configuration | structure schematic diagram at the time of using the atomic oscillator of this invention for the positioning system using a GPS satellite. It is a perspective view which shows the structure of a mobile body (automobile) provided with the atomic oscillator of this invention.

Hereinafter, an atomic resonance transition device, an atomic oscillator, an electronic device, and a moving body of the present invention will be described in detail based on embodiments shown in the accompanying drawings.
1. Atomic oscillator (quantum interference device)
First, the atomic oscillator of the present invention (the atomic oscillator including the atomic resonance transition apparatus of the present invention) will be described. In the following, an example in which the atomic resonance transition apparatus of the present invention is applied to an atomic oscillator will be described. However, the atomic resonance transition apparatus of the present invention is not limited to this, and in addition to an atomic oscillator, for example, a magnetic sensor, a quantum Applicable to memory and the like.

  FIG. 1 is a perspective view showing the atomic oscillator according to the first embodiment of the present invention, and FIG. 2 is a schematic diagram showing a schematic configuration of the atomic oscillator shown in FIG. FIG. 3 is a diagram for explaining the energy state of the alkali metal in the gas cell provided in the atomic oscillator shown in FIG. FIG. 4 shows the relationship between the frequency difference between the two lights from the light emitting part and the detection intensity at the light detecting part for the light emitting part and the light detecting part provided in the atomic oscillator shown in FIG. It is a graph. 5 is a longitudinal sectional view of the atomic oscillator shown in FIG. 1, and FIG. 6 is an enlarged sectional view of a part of FIG.

  1, 5, and 6, for convenience of explanation, the X axis, the Y axis, and the Z axis are illustrated as three axes orthogonal to each other, and the tip side of each illustrated arrow is indicated by “+ (Plus) ”and the base end side as“ − (minus) ”. In the following, for convenience of explanation, a direction parallel to the X axis is referred to as “X axis direction”, a direction parallel to the Y axis is referred to as “Y axis direction”, and a direction parallel to the Z axis is referred to as “Z axis direction”. Further, the + Z direction side (upper side in FIG. 5) is referred to as “upper”, and the −Z direction side (lower side in FIG. 5) is referred to as “lower”.

An atomic oscillator 1 shown in FIG. 1 is an atomic oscillator using a quantum interference effect. The atomic oscillator 1 using the quantum interference effect can be reduced in size as compared with an atomic oscillator using a double resonance phenomenon.
As shown in FIG. 1, the atomic oscillator 1 supports a first unit 2 (light emission side unit), a second unit 3 (light detection side unit), a package 5 for storing them, and a package 5. A wiring board 6 (board) and a control unit 7 mounted on the wiring board 6 are provided.

Here, as shown in FIGS. 1 and 2, the first unit 2 includes a light emitting portion 21 and a first package 22 (light emitting side package) that houses the light emitting portion 21.
The second unit 3 includes a gas cell 31, a light detection unit 32, a heater 33, a temperature sensor 34, a coil 35, and a second package 36 (light detection side package) that houses these.
The first unit 2 and the second unit 3 are electrically connected to the control unit 7 via wiring (not shown) of the wiring board 6 and are driven and controlled by the control unit 7.

First, the principle of the atomic oscillator 1 will be briefly described.
In the atomic oscillator 1, gaseous metal such as rubidium, cesium, and sodium (metal atom) is enclosed in a gas cell 31.
As shown in FIG. 3, the alkali metal has a three-level energy level, and is in three states, two ground states (ground states 1 and 2) having different energy levels, and an excited state. Can take. Here, the ground state 1 is a lower energy state than the ground state 2.

When two types of resonant lights 1 and 2 having different frequencies are irradiated onto such a gaseous alkali metal, the above-described gaseous alkali metal is irradiated with the frequency ω 1 of the resonant light 1 and the frequency ω 2 of the resonant light 2. In accordance with the difference (ω1-ω2), the light absorptivity (light transmittance) of the resonance lights 1 and 2 in the alkali metal changes.
When the difference (ω1−ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 matches the frequency corresponding to the energy difference between the ground state 1 and the ground state 2, the ground states 1 and 2 Each excitation to the excited state stops. At this time, both the resonant lights 1 and 2 are transmitted without being absorbed by the alkali metal. Such a phenomenon is called a CPT phenomenon or an electromagnetically induced transparency (EIT) phenomenon.
The light emitting unit 21 emits two types of light (resonant light 1 and resonant light 2) having different frequencies as described above toward the gas cell 31.

  For example, when the light emitting unit 21 fixes the frequency ω1 of the resonant light 1 and changes the frequency ω2 of the resonant light 2, the difference between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 (ω1-ω2). ) Coincides with the frequency ω 0 corresponding to the energy difference between the ground state 1 and the ground state 2, the detection intensity of the light detection unit 32 rises sharply as shown in FIG. Such a steep signal is detected as an EIT signal. This EIT signal has an eigenvalue determined by the type of alkali metal. Therefore, by using such an EIT signal as a reference, a highly accurate oscillator can be realized.

Hereinafter, each part of the atomic oscillator 1 will be described in detail sequentially.
(First unit)
As described above, the first unit 2 includes the light emitting unit 21 and the first package 22 that houses the light emitting unit 21.
[Light emitting part]
The light emitting unit 21 has a function of emitting excitation light that excites alkali metal atoms in the gas cell 31.
More specifically, the light emitting unit 21 emits two types of light (resonant light 1 and resonant light 2) having different frequencies as described above.

The frequency ω1 of the resonant light 1 can excite the alkali metal in the gas cell 31 from the ground state 1 to the excited state.
Further, the frequency ω2 of the resonance light 2 can excite the alkali metal in the gas cell 31 from the ground state 2 to the excited state.
The light emitting unit 21 is not particularly limited as long as it can emit the excitation light as described above. For example, a semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) can be used.
Further, such a light emitting part 21 is temperature-adjusted to a temperature (first temperature) different from a gas cell 31 described later, for example, about 30 ° C., by a temperature adjusting element (a heating resistor, a Peltier element, etc.) not shown. The

[First package (light emitting side package)]
The first package 22 houses the light emitting unit 21 described above.
As shown in FIG. 5, the first package 22 includes a base 221 (light emitting side base) and a lid 222 (light emitting side lid).
The base 221 supports the light emitting unit 21 directly or indirectly. In the present embodiment, the base body 221 has a plate shape and a circular shape in plan view.

The light emitting portion 21 (mounting component) is installed (mounted) on one surface (mounting surface) of the base 221. Further, as shown in FIG. 5, a plurality of terminals 223 (leads) protrude in the −X-axis direction on the other surface of the base 221. The plurality of terminals 223 are electrically connected to the light emitting unit 21 via wiring not shown.
As shown in FIG. 5, each of the plurality of terminals 223 extends in the X-axis direction, and is arranged in one direction (in this embodiment, the Y-axis direction) so as to be parallel to each other.

The constituent material of the base 221 is not particularly limited, and for example, a ceramic material, a metal material, a resin material, or the like can be used, but a metal material is preferably used. Thereby, when the cover body 222 is comprised with a metal material, the base | substrate 221 and the cover body 222 can be airtightly joined comparatively easily and reliably by welding.
A lid body 222 that covers the light emitting portion 21 on the base body 221 is joined to the base body 221.

The lid 222 has a bottomed cylindrical shape with one end opened. In the present embodiment, the cylindrical portion of the lid 222 has a cylindrical shape.
The opening at one end of the lid 222 is closed by the base 221 described above.
A window 23 is provided at the other end of the lid 222, that is, at the bottom opposite to the opening of the lid 222.
The window portion 23 is provided on the optical axis a between the gas cell 31 and the light emitting portion 21.

And the window part 23 has transparency with respect to the excitation light mentioned above. Thereby, the light emitting part 21 can be accommodated in the first package 22 while allowing the excitation light to be emitted from the light emitting part 21 to the outside of the first package 22.
In this embodiment, the window part 23 is comprised with the lens. Thereby, the excitation light LL can be irradiated to the gas cell 31 without waste.

Moreover, the window part 23 has a function which makes the excitation light LL parallel light. Thereby, it is possible to easily and reliably prevent the excitation light LL from being reflected from the inner wall of the gas cell 31 while increasing the amount of the alkali metal irradiated with the excitation light LL. Therefore, resonance of excitation light in the gas cell 31 is preferably generated, and as a result, the oscillation characteristics of the atomic oscillator 1 can be enhanced.
The window 23 is not limited to a lens as long as it has transparency to excitation light. For example, the window 23 may be an optical component other than a lens such as a polarizing plate, a λ / 4 wavelength plate, and a neutral density filter. Alternatively, it may be a simple light-transmitting plate member. Moreover, these optical components should just be provided between the light emission part 21 and the gas cell 31 mentioned later, for example, may be provided between the window part 37 and the light emission part 21, Further, it may be provided between the first package 22 and the second package 36.

  The constituent material other than the window portion 23 of the lid 222 is not particularly limited, and for example, a ceramic material, a metal material, a resin material, or the like can be used, but a metal material is preferably used, It is more preferable to use an Fe—Ni alloy such as Kovar or Permalloy, and it is more preferable to use Kovar. Thereby, the base body 221 and the lid body 222 can be joined relatively easily and reliably in an airtight manner by welding.

  The lid 222 may be composed of one type of material, or may be configured by mixing or laminating two or more types of materials. Moreover, when parts other than the window part 23 of the cover body 222 are comprised with the material which has a transmittance | permeability with respect to excitation light, parts other than the window part 23 of the cover body 222 and the window part 23 are formed integrally. can do. Further, when the portion other than the window portion 23 of the lid 222 is made of a material that is not transmissive to the excitation light, the portion other than the window portion 23 of the lid 222 and the window portion 23 are separated. These may be formed and bonded by a known bonding method.

Moreover, it is preferable that the base body 221 and the lid 222 are airtightly joined. That is, it is preferable that the inside of the first package 22 is an airtight space. Thereby, the inside of the 1st package 22 can be made into a pressure-reduced state (state decompressed from atmospheric pressure) or an inert gas enclosure state, As a result, the characteristic of the atomic oscillator 1 can be improved.
The method for joining the base 221 and the lid 222 is not particularly limited, and for example, brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.), and the like can be used.

A joining member for joining these may be interposed between the base 221 and the lid 222.
In addition, the first package 22 may contain components other than the light emitting unit 21 described above.
For example, the first package 22 may contain a temperature adjustment element, a temperature sensor, or the like that adjusts the temperature of the light emitting unit 21. Examples of such temperature adjusting elements include heating resistors (heaters), Peltier elements, and the like.
The first package 22 as described above is held by the package 5 to be described later so that the base 221 is disposed on the side opposite to the second package 36.

(Second unit)
As described above, the second unit 3 includes the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, the coil 35, and the second package 36 that houses them.
[Gas cell]
The gas cell 31 is filled with gaseous alkali metals such as rubidium, cesium, and sodium. Further, in the gas cell 31, a rare gas such as neon or argon, an inert gas such as nitrogen, or the like is sealed as a buffer gas as necessary.
As shown in FIG. 6, the gas cell 31 includes a main body portion 311 having columnar through holes and a pair of window portions 312 and 313 that block both openings of the through holes. Thereby, the internal space S1 in which the alkali metal as described above is enclosed is formed.

  The material constituting the main body 311 is not particularly limited, and examples thereof include a metal material, a resin material, a glass material, a silicon material, and a crystal. The hermetic bonding with the window portions 312 and 313 is anodic bonding and direct bonding. From the viewpoint of ease of use, it is preferable to use a glass material or a silicon material. Further, by configuring the main body portion 311 with a silicon material, the main body portion 311 can be formed easily and with high accuracy by fine processing using the MEMS technology.

Each of the window portions 312 and 313 has transparency to the excitation light from the light emitting portion 21 described above. One window 313 transmits excitation light incident into the gas cell 31, and the other window 312 transmits excitation light emitted from the gas cell 31.
Therefore, the material constituting the window portions 312 and 313 of the gas cell 31 is not particularly limited as long as it has transparency to the excitation light as described above, and examples thereof include glass materials and crystal.

The window portions 312 and 313 are airtightly joined to the main body portion 311. Thereby, internal space S1 of the gas cell 31 can be made into airtight space.
The joining method of the main body 311 and the windows 312 and 313 of the gas cell 31 is determined according to these constituent materials, and is not particularly limited. For example, a joining method using an adhesive, a direct joining method, an anode A bonding method or the like can be used.
The temperature of the gas cell 31 as described above is adjusted by the heater 33 to a temperature (second temperature) different from that of the light emitting unit 21 described above, for example, about 70 ° C.

[Photodetection section]
The light detection unit 32 has a function of detecting the intensity of the excitation light LL (resonance light 1 and 2) transmitted through the gas cell 31.
The light detector 32 is not particularly limited as long as it can detect the excitation light as described above. For example, a photodetector (light receiving element) such as a solar cell or a photodiode can be used.

[heater]
The heater 33 has a function of heating the above-described gas cell 31 (more specifically, an alkali metal in the gas cell 31). Thereby, the alkali metal in the gas cell 31 can be maintained in a gaseous state with an appropriate concentration.
The heater 33 generates heat when energized, and includes heating resistors 331 and 332 provided on the outer surface of the gas cell 31, as shown in FIG. Such heat generating resistors 331 and 332 are formed using, for example, a chemical vapor deposition method (CVD) such as plasma CVD or thermal CVD, a dry plating method such as vacuum vapor deposition, a sol-gel method, or the like.

Here, the heating resistor 331 is provided on the window 312 of the gas cell 31, and the heating resistor 332 is provided on the window 313 of the gas cell 31.
The heating resistors 331 and 332 are made of a material having transparency to excitation light, specifically, for example, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), In ₃ O ₃ , SnO ₂ , Sb-containing SnO. _2. It is comprised with transparent electrode materials, such as oxides, such as Al containing ZnO.

The heater 33 is not limited to the above-described configuration as long as it can heat the gas cell 31, and may be non-contact with the gas cell 31. Further, the gas cell 31 may be heated using a Peltier element instead of the heater 33 or in combination with the heater 33.
The heater 33 as described above is electrically connected to a temperature control unit 72 of the control unit 7 described later and energized.

[Temperature sensor]
The temperature sensor 34 detects the temperature of the heater 33 or the gas cell 31. Based on the detection result of the temperature sensor 34, the amount of heat generated by the heater 33 is controlled. Thereby, the alkali metal atom in the gas cell 31 can be maintained at a desired temperature.

The installation position of the temperature sensor 34 is not particularly limited, and may be, for example, on the heater 33 or on the outer surface of the gas cell 31.
The temperature sensor 34 is not particularly limited, and various known temperature sensors such as a thermistor and a thermocouple can be used.
The temperature sensor 34 as described above is electrically connected to a temperature control unit 72 of the control unit 7 which will be described later via a wiring (not shown).

[coil]
The coil 35 has a function of generating a magnetic field when energized.
In the present embodiment, the coil 35 is a solenoid type coil that has a cylindrical shape, the axis of which is arranged along the X-axis direction, and surrounds the gas cell 31. Such a coil 35 generates a magnetic field along the X-axis direction in the gas cell 31. Note that the coil 35 is not limited to the solenoid type, and may be a Helmholtz type arranged to face each other via the gas cell 31.

  The coil 35 normally constitutes an “excitation coil” that is supplied with a direct current from a power source 4 to be described later to generate a direct-current magnetic field. This DC magnetic field is applied to the alkali metal in the gas cell 31. Thereby, by Zeeman splitting, the gap between different energy levels in which the alkali metal is degenerated can be widened to improve the resolution. As a result, the accuracy of the oscillation frequency of the atomic oscillator 1 can be increased. Hereinafter, a DC magnetic field for causing Zeeman splitting of such an alkali metal is also referred to as an “excitation magnetic field”. The direct current for generating the excitation magnetic field is also referred to as “excitation current”.

  Further, when necessary, the coil 35 is supplied with a current in which an excitation current and an alternating current that decays with time (hereinafter also referred to as “demagnetization current” or “attenuation current”) are superposed from a power source 4 described later. A “demagnetizing coil” for generating a demagnetizing magnetic field is configured. Accordingly, the second package 36 can be demagnetized when necessary. In particular, since the demagnetizing magnetic field component is superimposed on the DC magnetic field component and the alternating magnetic field component that decays with time, the second package 36 is magnetized by the demagnetizing magnetic field from the coil 35 by the DC magnetic field from the coil 35. It can be demagnetized with a slight amount of magnetization similar to Therefore, when an exciting magnetic field is generated from the coil 35 after demagnetizing the second package 36, a change in the amount of magnetization of the second package 36 over time due to the exciting magnetic field from the coil 35 can be prevented or suppressed. . As a result, the strength of the magnetic field applied to the alkali metal in the gas cell 31 can be stabilized, and the long-term stability of the frequency can be improved.

Further, since the coil 35, which is an exciting coil for generating an exciting magnetic field, also serves as a degaussing coil for generating a demagnetizing magnetic field, the number of parts can be reduced, and the atomic oscillator 1 can be reduced in size and cost.
Here, the coil 35 is disposed between the alkali metal in the gas cell 31 and the second package 36. As a result, the coil 35 that is an exciting coil can also be used as a degaussing coil.
The exciting magnetic field and the demagnetizing magnetic field will be described in detail later together with the magnetic field control unit 73 and the power source 4.
The coil 35 as described above is electrically connected to a magnetic field control unit 73 of the control unit 7 (described later) via a wiring (not shown) and a power supply 4 (described later) (see FIG. 7).

[Second package (light detection side package)]
The second package 36 houses the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 described above.
The second package 36 has magnetic shielding properties and constitutes a “shielding portion” that shields the alkali metal in the gas cell 31 from an external magnetic field. When the package 5 described later has a magnetic shielding property and constitutes an “outer shielding portion” of the “shielding portion”, the second package 36 disposed inside the package 5 has an “inner shielding” of the “shielding portion”. Part ".

The second package 36 can be configured in the same manner as the first package 22 of the first unit 2 described above.
Specifically, as shown in FIGS. 5 and 6, the second package 36 includes a base 361 (light detection side base) and a lid 362 (light detection side lid).
The base 361 directly or indirectly supports the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35. In the present embodiment, the base 361 has a disk shape.

  On one surface (mounting surface) of the base 361, the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 (a plurality of mounting components) are installed (mounted). In the present embodiment, the gas cell 31, the light detection unit 32, and the heater 33 are mounted on the base 361 through the substrate 38. A plurality of terminals 363 (leads) protrude in the + X axis direction on the other surface of the base 361. The plurality of terminals 363 are electrically connected to the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 through a wiring (not shown).

Each of the plurality of terminals 363 extends in the X-axis direction, and is arranged in one direction (Y-axis direction in the present embodiment) so as to be parallel to each other. Note that the arrangement of the plurality of terminals 363 is not limited to this and is arbitrary.
As the constituent material of the base 361, a material having magnetic shielding properties is used, and examples thereof include soft magnetic materials such as Fe and various iron-based alloys (silicon iron, permalloy, amorphous, sendust, kovar), and the like. Among these, from the viewpoint of excellent magnetic shielding properties, it is preferable to use an Fe—Ni-based alloy such as Kovar or Permalloy, and from the viewpoint that the airtight joining between the base 361 and the lid 362 can be easily and reliably performed by welding. It is more preferable to use.
A lid 362 that covers the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 is joined to the base 361.

The lid body 362 has a bottomed cylindrical shape with one end opened. In the present embodiment, the cylindrical part of the lid 362 has a cylindrical shape.
The opening at one end of the lid 362 is closed by the base 361 described above.
A window 37 is provided at the other end of the lid 362, that is, at the bottom opposite to the opening of the lid 362.
This window part 37 is provided on the optical axis a between the gas cell 31 and the light emitting part 21.

  And the window part 37 has transparency with respect to the excitation light mentioned above. Accordingly, the gas cell 31 and the light detection unit 32 can be accommodated in the second package 36 while allowing the excitation light from the light emitting unit 21 to enter the second package 36. Therefore, by using the second package 36 in combination with the first package 22 as described above, the light emitting part is secured while securing the optical path of the excitation light from the light emitting part 21 to the light detecting part 32 via the gas cell 31. 21 and the gas cell 31 can be housed in separate packages that are not in contact with each other.

In this embodiment, the window part 37 is comprised with the plate-shaped member which has a light transmittance. And the window part 37 is joined to parts other than the window part 37 of the cover body 362 by the well-known joining method.
The window portion 37 is not limited to a light-transmitting plate member as long as it has transparency to excitation light. For example, the window portion 37 is an optical component such as a lens, a polarizing plate, or a λ / 4 wavelength plate. May be.

Any constituent material other than the window 37 of the lid 362 may be used as long as it has magnetic shielding properties, and the same material as the constituent material of the base 361 described above can be used.
The base 361 and the lid 362 are preferably joined in an airtight manner. That is, it is preferable that the inside of the second package 36 is an airtight space. Thereby, the inside of the 2nd package 36 can be made into a pressure reduction state (state pressure-reduced from atmospheric pressure) or an inert gas enclosure state, As a result, the characteristic of the atomic oscillator 1 can be improved.

The method for joining the base 361 and the lid 362 is not particularly limited, and for example, brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.), and the like can be used.
Note that a bonding member for bonding them may be interposed between the base 361 and the lid 362.

Further, at least the gas cell 31 and the light detector 32 need only be housed in the second package 36, and components other than the gas cell 31, the light detector 32, the heater 33, the temperature sensor 34, and the coil 35 described above. May be stored.
The second package 36 as described above is held by the package 5 to be described later so that the base 361 is disposed on the side opposite to the first package 22.

(package)
The package 5 has a function of accommodating the first package 22 and the second package 36 described above.
The package 5 has an internal space S in which the first unit 2 and the second unit 3 are stored in a state of being spaced apart from each other, and the internal space S is in a state of being depressurized from atmospheric pressure. Yes. Thereby, it is possible to suppress heat transfer due to heat conduction and convection between the package 5 and the first unit 2 and the second unit 3 and between the first unit 2 and the second unit 3.
Specifically, as shown in FIG. 5, the package 5 includes a main body 50 having a recess 51 that opens upward, and a lid 54 that seals the recess 51.
The first package 22 and the second package 36 are installed in the recess 51 of the main body 50.

  The recess 51 has a shape that regulates the positions and postures of the first package 22 and the second package 36. Thereby, by positioning the first package 22 and the second package 36 in the recess 51 of the package 5, the optical system including the light emitting unit 21 and the light detecting unit 32 can be positioned. Therefore, the installation of the first package 22 and the second package 36 with respect to the package 5 can be facilitated.

Here, the recess 51 extends in the X-axis direction, the first package 22 is disposed on one end side (left side in FIG. 5), and on the other end side (right side in FIG. 5). The second package 36 is disposed.
In addition, the first package 22 and the second package 36 are arranged so that the axis of the cylindrical lid body 222 and the lid body 362 are parallel to the extending direction of the recess 51 (X-axis direction). Thereby, the first package 22 and the second package 36 are arranged such that the axes of the lid 222 and the lid 362 are aligned or parallel to each other.

In this embodiment, the cross section of the recess 51 is rectangular.
Further, a support portion 52 (first support portion) that supports the base body 221 of the first package 22 is provided on one end portion side (left side in FIG. 5) of the main body 50, and the other end portion (FIG. 5). A support portion 53 (second support portion) that supports the base 361 of the second package 36 is provided on the right side in the middle.

  As described above, the support portion 52 supports the base body 221, and the support portion 53 facing the support portion 52 supports the base body 361, whereby the contact portion between the first package 22 and the package 5, and the second package 36. And the contact portion between the package 5 and the package 5 can be increased. Therefore, the heat conduction through the package 5 between the first package 22 and the second package 36 can be more effectively suppressed.

  The lid 222 and the lid 362 are not in contact with the package 5, respectively. Thereby, the heat conduction through the package 5 between the first package 22 and the second package 36 can be more effectively suppressed. In particular, since the cross section of the recess 51 is rectangular, the cylindrical portions of the lids 222 and 362 are respectively cylindrical, so that the relatively small space between the side surfaces of the lids 222 and 362 and the package 5 is relatively small. A large gap can be formed. As a result, heat conduction from the lids 222 and 362 to the package 5 can be suppressed to an extremely low level. Further, even if the side surfaces of the lids 222 and 362 are in contact with the package 5, the contact area can be reduced.

  Here, the support part 52 has an installation surface parallel to the Y axis and the Z axis. The surface opposite to the lid 222 of the base body 221 of the first package 22 is in contact with or close to the installation surface. Thereby, the position and attitude | position of the 1st package 22 with respect to the package 5 can be controlled. The base body 221 can be fixed to the support portion 52 using an adhesive, for example.

  Further, the support portion 52 is formed with a plurality of through holes 521 through which the plurality of terminals 223 of the first package 22 described above are inserted. That is, the support part 52 has a shape like a socket to which the first package 22 is attached. Also by this, the position and attitude of the first package 22 with respect to the package 5 can be regulated. The plurality of terminals 223 can be fixed to the support portion 52 by, for example, solder.

The plurality of terminals 223 pass through the plurality of through holes 521. Thereby, the tip of each terminal 223 protrudes from the package 5.
Here, the plurality of through holes 521 are provided corresponding to the plurality of terminals 223, respectively, extend in the X-axis direction, and are arranged in the Y-axis direction. Accordingly, portions of the plurality of terminals 223 protruding from the package 5 are also arranged in the Y-axis direction.

  Similarly, the support part 53 has an installation surface parallel to the Y axis and the Z axis. The surface opposite to the lid 362 of the base body 361 of the second package 36 is in contact with or close to this installation surface. Thereby, the position and attitude of the second package 36 relative to the package 5 can be regulated. Note that the base 361 can be fixed to the support 53 using an adhesive, for example.

The support portion 53 has a plurality of through holes 531 through which the plurality of terminals 363 of the second package 36 described above are inserted. That is, the support portion 53 has a shape like a socket to which the second package 36 is attached. Also by this, the position and attitude of the second package 36 with respect to the package 5 can be regulated. The plurality of terminals 363 can be fixed to the support portion 53 by, for example, solder.
The plurality of terminals 363 pass through the plurality of through holes 531. Thereby, the tip of each terminal 363 protrudes from the package 5.

Here, the plurality of through holes 531 are provided corresponding to the plurality of terminals 363, respectively, extend in the X-axis direction, and are arranged in the Y-axis direction. Accordingly, portions of the plurality of terminals 363 protruding from the package 5 are also arranged in the Y-axis direction.
A lid 54 that closes the opening of the recess 51 is joined to the main body 50.
The lid 54 has a flat plate shape.
Moreover, it is preferable that the main body 50 and the cover body 54 are airtightly joined. That is, the inside of the package 5 is preferably an airtight space. Thereby, the inside of the package 5 can be made into a pressure-reduced state (state pressure-reduced from atmospheric pressure) or an inert gas enclosure state.

The method for joining the main body 50 and the lid 54 is not particularly limited, and for example, brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.), and the like can be used.
The constituent materials of the main body 50 and the lid body 54 of the package 5 are not particularly limited, and examples thereof include metal materials, resin materials, and ceramic materials.

  When a metal material is used as the constituent material of the main body 50 and the lid body 54, the main body 50 and the lid body 54 can be joined together in a relatively simple and reliable manner by welding. In particular, as such a metal material, it is preferable to use soft magnetic materials such as Fe and various iron-based alloys (silicon iron, permalloy, amorphous, sendust, kovar), and use Fe-Ni-based alloys such as kovar and permalloy. Is more preferable, and it is more preferable to use permalloy. Thereby, the magnetic shielding property of the package 5 can be made excellent. Here, when the package 5 has magnetic shielding properties, the package 5 constitutes an “outer shielding portion” of the “shielding portion”.

On the other hand, when a non-metallic material such as a resin material or a ceramic material is used as the constituent material of the main body 50 and the lid body 54, the heat conduction through the package 5 between the first package 22 and the second package 36 is reduced. be able to. As a result, thermal interference between the light emitting part 21 and the gas cell 31 can be effectively prevented or suppressed.
Although it does not specifically limit as a resin material which comprises the package 5, For example, polyolefin, such as polyethylene and ethylene-vinyl acetate copolymer (EVA), acrylic resin, acrylonitrile-butadiene-styrene copolymer (ABS resin), Acrylonitrile-styrene copolymer (AS resin), polyethylene terephthalate (PET), polyether, polyether ketone (PEK), polyether ether ketone (PEEK), styrene, polyolefin, polyvinyl chloride, polyurethane, polyester , Polyamide, polybutadiene, trans polyisoprene, fluororubber, chlorinated polyethylene, and other thermoplastic elastomers, epoxy resins, phenol resins, urea resins, melamine resins, unsaturated polyesters, Ricone resin, polyurethane, etc., or copolymers, blends, polymer alloys, etc. mainly composed of these are used, and one or more of these are used in combination (for example, as a laminate of two or more layers). be able to.

The ceramic material constituting the package 5 is not particularly limited. For example, various glasses, oxide ceramics such as alumina, silica, titania, zirconia, yttria, calcium phosphate, silicon nitride, aluminum nitride, and nitride Examples thereof include nitride ceramics such as titanium and boron nitride, carbide ceramics such as graphite and tungsten carbide, and other ferroelectric materials such as barium titanate, strontium titanate, PZT, PLZT, and PLLZT.
The package 5 as described above is supported by the wiring board 6.

(Wiring board)
The wiring board 6 has wiring (not shown), and through such wiring, electronic components such as the control unit 7 mounted on the wiring board 6, the plurality of terminals 223 of the first package 22, and the plurality of terminals of the second package. A function of electrically connecting the terminal 363 is provided.
The wiring board 6 also has a function of supporting the package 5 through the plurality of terminals 223 and the plurality of terminals 363.

In the present embodiment, as shown in FIG. 5, the wiring substrate 6 has a through hole 61 that penetrates in the thickness direction.
The package 5 is inserted into the through hole 61. Thereby, compared with the case where the package 5 is mounted on the surface of the wiring board 6, the overall height of the apparatus can be reduced. Note that the through hole 61 may be omitted, and in that case, the package 5 may be disposed on one surface of the wiring board 6.

A plurality of terminals 62 and a plurality of terminals 63 are provided on one surface of the wiring board 6 around the through hole 61.
The plurality of terminals 62 are provided corresponding to the plurality of terminals 223 of the first package 22 described above. A plurality of corresponding terminals 223 are joined to the plurality of terminals 62, respectively.

The plurality of terminals 63 are provided corresponding to the plurality of terminals 363 of the second package 36 described above. A plurality of corresponding terminals 363 are joined to the plurality of terminals 63, respectively.
With these bondings, the package 5 is supported on the wiring board 6 via the plurality of terminals 223 and the plurality of terminals 363, and the plurality of terminals 223 are electrically connected to the plurality of terminals 62, respectively. Are electrically connected to the plurality of terminals 63, respectively.

  The joining method between the terminal 223 and the terminal 62 and the joining method between the terminal 363 and the terminal 63 are not particularly limited as long as they can be joined while ensuring the electrical continuity of the joint portion. And a joining method using a solder, a joining method using an anisotropic conductive adhesive, and the like. Moreover, when the terminal 223 and the terminal 62 are comprised like a crimp terminal, the terminal 223 and the terminal 62 can also be joined by crimping. Similarly, when the terminal 363 and the terminal 63 are configured as a crimp terminal, the terminal 363 and the terminal 63 can be joined by crimping.

Such a plurality of terminals 223 and 363 are each electrically connected to the control unit 7 via wiring not shown.
As such a wiring board 6, various printed wiring boards can be used. From the viewpoint of securing rigidity necessary to support the package 5, a board having a rigid portion, for example, a rigid board or a rigid flexible board. Etc. are preferably used.

Even when a wiring board having no rigid portion (for example, a flexible board) is used as the wiring board 6, for example, by bonding a reinforcing member for improving rigidity to the wiring board, The rigidity required to support the package 5 can be ensured.
The controller 7 is installed on one surface of the wiring board 6 as described above. Note that electronic components other than the control unit 7 may be mounted on the wiring board 6.

[Control unit]
The control unit 7 illustrated in FIG. 2 has a function of controlling the heater 33, the coil 35, and the light emitting unit 21, respectively.
In the present embodiment, the control unit 7 is configured by an IC (Integrated Circuit) chip mounted on the wiring board 6.
Such a control unit 7 includes an excitation light control unit 71 that controls the frequencies of the resonance lights 1 and 2 of the light emitting unit 21, a temperature control unit 72 that controls the temperature of the alkali metal in the gas cell 31, and the gas cell 31. And a magnetic field control unit 73 that controls the magnetic field to be applied.

  The excitation light control unit 71 controls the frequencies of the resonance lights 1 and 2 emitted from the light emission unit 21 based on the detection result of the light detection unit 32 described above. More specifically, the excitation light control unit 71 emits light from the light emitting unit 21 so that (ω1-ω2) detected by the light detection unit 32 described above becomes the frequency ω0 specific to the alkali metal described above. The frequency of the resonant lights 1 and 2 is controlled. Further, the excitation light control unit 71 controls the center frequency of the resonance lights 1 and 2 emitted from the light emitting unit 21.

Further, the temperature control unit 72 controls energization to the heater 33 based on the detection result of the temperature sensor 34. Thereby, the gas cell 31 can be maintained within a desired temperature range.
The magnetic field control unit 73 has a function of controlling the magnetic field generated by the coil 35.
The magnetic field control unit 73 is connected to the power source 4 that supplies current to the coil 35, and controls the magnetic field generated by the coil 35 by controlling the driving of the power source 4.

The power supply 4 outputs a current supplied to the coil 35.
In particular, the power source 4 is configured to be able to generate an exciting current and a demagnetizing current simultaneously. In the present embodiment, the power source 4 is configured to output a current obtained by superimposing the excitation current and the demagnetization current when the excitation current and the demagnetization current are generated simultaneously. Thereby, a demagnetizing magnetic field as described above can be generated.

Hereinafter, the magnetic field control unit 73 and the power supply 4 will be described in detail.
FIG. 7 is a block diagram for explaining the magnetic field control unit shown in FIG.
As shown in FIG. 7, the power supply 4 includes an excitation current generator 41 (DC power supply) that generates an excitation current that is a DC current and a demagnetization current (attenuation AC) that is an alternating current that decays with time. A current generator 42 (AC power supply) and a current superimposing unit 43 that superimposes an exciting current and a demagnetizing current are included.

The exciting current generator 41 is constituted by, for example, a DC power supply circuit (constant current circuit). The excitation current generator 41 is preferably configured so that the current value of the generated excitation current can be adjusted. Thereby, the frequency characteristic of the atomic oscillator 1 can be adjusted when desired.
The demagnetizing current generator 42 is configured to include, for example, an AC power supply circuit and a variable transformer or a variable resistor. The frequency of the AC power supply circuit included in the demagnetizing current generator 42 may be variable.
The current superimposing unit 43 is composed of an adder, for example.

With such a relatively simple configuration, it is possible to realize the power supply 4 that can generate a current in which an excitation current and a demagnetization current are superimposed. A demagnetizing current path between the demagnetizing current generator 42 and the current superimposing unit 43 may be provided with a switch that can be opened and closed.
The magnetic field control unit 73 that controls the power source 4 can switch between a degaussing mode that supplies a current obtained by superimposing an exciting current and a demagnetizing current to the coil 35 and a normal mode that supplies the exciting current to the coil 35. It is. Thereby, the 2nd package 36 can be demagnetized at arbitrary timings.

  In the demagnetization mode, the magnetic field control unit 73 operates the excitation current generation unit 41 and the demagnetization current generation unit 42 simultaneously. More specifically, the magnetic field control unit 73 generates an excitation current that is a steady current from the excitation current generation unit 41 and also generates a demagnetization current that is an alternating current that decays with time from the demagnetization current generation unit 42. As a result, a current obtained by superimposing the exciting current and the demagnetizing current is output from the power supply 4. The coil 35 is supplied with a current obtained by superimposing an excitation current and a demagnetizing current from the power supply 4 and generates a demagnetizing magnetic field. As a result, a demagnetizing magnetic field in which a direct-current magnetic field component and an alternating-current magnetic field component that decays with time can be generated from the coil 35 constituted by one coil.

  In such a demagnetizing magnetic field, a direct-current magnetic field component and an alternating-current magnetic field component that decays with time are superimposed. Therefore, the second package 36 is magnetized by the demagnetizing magnetic field from the coil 35 by the direct-current magnetic field from the coil 35. It is possible to demagnetize in a state in which a slight amount of magnetization similar to that described above remains. Therefore, when an exciting magnetic field is generated from the coil 35 after demagnetizing the second package 36, a change in the amount of magnetization of the second package 36 over time due to the exciting magnetic field from the coil 35 can be prevented or suppressed. . As a result, the strength of the magnetic field applied to the alkali metal in the gas cell 31 can be stabilized, and the long-term stability of the frequency can be improved.

  Here, the DC magnetic field component of the degaussing magnetic field is based on the excitation current, and the AC magnetic field component of the degaussing magnetic field is based on the demagnetizing current. Therefore, the DC magnetic field component of the demagnetizing magnetic field in the second package 36 is equal to or close to the exciting magnetic field. As a result, the magnetization amount remaining in the second package 36 after demagnetization can be set to the same magnetization amount as that which is magnetized by the DC magnetic field from the coil 35 in the normal mode. Therefore, when a DC magnetic field is generated from the coil 35 in the normal mode after demagnetizing the second package 36 in the demagnetization mode, the change in the amount of magnetization of the second package 36 over time due to the magnetic field from the coil 35 is reduced. (Substantially disappear). The current value of the excitation current in the degaussing mode is preferably equal to the current value of the excitation current in the normal mode, but if the deviation from the current value of the excitation current in the normal mode is 10% or less, the normal mode The current value of the excitation current may be different.

On the other hand, in the normal mode, the magnetic field controller 73 operates the exciting current generator 41 with the demagnetizing current generator 42 stopped. More specifically, the magnetic field control unit 73 generates an excitation current that is a steady current from the excitation current generation unit 41 and sets the current value of the current generated from the demagnetization current generation unit 42 to zero. That is, the magnetic field control unit 73 stops the demagnetizing current generation unit 42 while maintaining the operation state of the excitation current generation unit 41 when shifting from the demagnetization mode to the normal mode. As a result, only the excitation current is output from the power supply 4. The coil 35 is supplied with an excitation current from the power supply 4 and generates an excitation magnetic field. Thereby, as described above, the alkali metal in the gas cell 31 can be Zeeman-split, and the accuracy of the oscillation frequency of the atomic oscillator 1 can be improved.
When a switch that can be opened and closed is provided between the demagnetizing current generator 42 and the current superimposing unit 43, even if the operating states of the excitation current generating unit 41 and the demagnetizing current generating unit 42 are the same as the demagnetizing mode. The normal mode can be set by opening the switch.

Hereinafter, the improvement in long-term frequency stability by the demagnetization mode as described above will be described more specifically.
FIG. 8A is a graph showing a change over time of the current flowing in the exciting coil in the conventional demagnetization mode, and FIG. 8B is a transition from the demagnetization mode using the current shown in FIG. 8A to the normal mode. It is a graph which shows a time-dependent change of the magnetization amount of the shield part at the time of doing. 9A is a graph showing a change over time of the current flowing from the power source shown in FIG. 7 to the exciting coil (demagnetizing coil) in the degaussing mode, and FIG. 9B is a current shown in FIG. 9A. 6 is a graph showing a change over time in the amount of magnetization of a shield part when a demagnetization mode using a transition to a normal mode. FIG. 10 is a graph showing a modification of the change over time of the current flowing from the power source shown in FIG. 7 to the exciting coil (demagnetizing coil) in the demagnetizing mode.

In the conventional demagnetization mode, demagnetization is performed using an alternating current whose current value converges to zero as shown in FIG. If an alternating current as shown in FIG. 8A is supplied to the coil 35 and the degaussing mode is performed, as shown in FIG. 8B, the magnetization amount of the second package 36 immediately after the end of the degaussing mode is It becomes zero. Thereafter, when the mode is switched to the normal mode, the second package 36 is gradually magnetized by the exciting magnetic field from the coil 35. This magnetization is stabilized by an amount B1 corresponding to the intensity of the excitation magnetic field from the coil 35, but it takes a long time from several hours to several months for the stabilization. Therefore, the fluctuation of the magnetization amount of the second package 36 during that period affects the frequency long-term stability, and the frequency long-term stability is lowered.
FIG. 8 shows an example in which the magnetization of the second package 36 before the start of the demagnetization mode has the same polarity as the magnetization of the second package 36 in the normal mode, but before the start of the demagnetization mode. In the case where the magnetization of the second package 36 at the same polarity is opposite in polarity to the magnetization of the second package 36 in the normal mode, the long-term stability of the frequency similarly decreases.

On the other hand, in the degaussing mode according to the present invention, the alternating current is used in which the current value converges to a value I1 (current value of the exciting current in this embodiment) different from zero as shown in FIG. Therefore, when an alternating current as shown in FIG. 9A is supplied to the coil 35 to perform the degaussing mode, as shown in FIG. 9B, the magnetization amount of the second package 36 immediately after the end of the degaussing mode is The value B1 is different from zero. This value B1 coincides with or approximates the magnetization amount of the second package 36 that is stabilized by the excitation magnetic field from the coil 35 in the normal mode. Therefore, even when the mode is switched to the normal mode after the degaussing mode, the magnetization amount of the second package 36 is not changed by the exciting magnetic field from the coil 35 and is stabilized. That is, in the normal mode, the magnetization amount of the second package 36 can be stabilized immediately after the degaussing mode ends.
For this reason, the atomic oscillator 1 can stabilize the strength of the magnetic field applied to the alkali metal in the gas cell 31 and improve the long-term stability of the frequency.

  FIG. 9 illustrates an example in which the magnetization of the second package 36 before the start of the demagnetization mode has the same polarity as the magnetization of the second package 36 in the normal mode, but before the start of the demagnetization mode. In the case where the magnetization of the second package 36 is opposite in polarity to the magnetization of the second package 36 in the normal mode, the long-term stability of the frequency can be improved similarly.

The timing for performing the demagnetization mode as described above is not particularly limited, but is, for example, before using the oscillation signal of the atomic oscillator 1 for a long period of time. In addition, even after the normal mode is once performed, if the set value of the excitation current can be adjusted, the demagnetization mode may be performed after the adjustment. In addition, even after the normal mode is once performed, the demagnetization mode may be performed when the magnetization amount of the second package 36 exceeds a predetermined value, or the magnetization amount of the second package 36 may be reduced. Regardless, the demagnetization mode may be performed every predetermined time.
Further, the time length of the degaussing mode, in other words, the time length from when the demagnetizing current is generated until the current value becomes zero is not particularly limited, but is, for example, several seconds to several tens of seconds.

  Further, a preliminary demagnetization mode, which is a demagnetization mode similar to the conventional one, may be performed before the demagnetization mode as described above. In this case, as shown in FIG. 10, the power supply 4 outputs an alternating current that converges to a value I1 that is different from zero after outputting an alternating current that converges to zero. Thereby, even if the magnetization amount of the 2nd package 36 is large, the 2nd package 36 can be demagnetized to a desired state easily and reliably. Therefore, the variation in the magnetization amount of the second package 36 between products can be reduced.

  According to the atomic oscillator 1 of the present embodiment as described above, since the demagnetizing magnetic field is superimposed on the DC magnetic field component and the AC magnetic field component that decays with time, the second package 36 is applied by the demagnetizing magnetic field from the coil 35. Can be demagnetized in a state in which a slight amount of magnetization similar to that magnetized by the DC magnetic field from the coil 35 remains. Therefore, when an exciting magnetic field is generated from the coil 35 after demagnetizing the second package 36, a change in the amount of magnetization of the second package 36 over time due to the exciting magnetic field from the coil 35 can be prevented or suppressed. . As a result, the strength of the magnetic field applied to the alkali metal in the gas cell 31 can be stabilized, and the long-term stability of the frequency can be improved.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 11 is an enlarged sectional view showing a part of the atomic oscillator according to the second embodiment of the present invention, and FIG. 12 is a block diagram for explaining a magnetic field control unit of the atomic oscillator shown in FIG. FIG. 13 is a graph showing the change with time of the current flowing in the degaussing coil in the degaussing mode from the power source shown in FIG.
This embodiment is the same as the first embodiment described above except that the degaussing coil is composed of two coils.

In the following description, the second embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted. In FIG. 11 and FIG. 12, the same reference numerals are given to the same configurations as those in the above-described embodiment.
The atomic oscillator 1A of the present embodiment is the same as the atomic oscillator 1 of the first embodiment described above except that the coil 39 is added and the current superimposing unit 43 is omitted.

An atomic oscillator 1A shown in FIG. 11 includes a coil 39 and a power source 4A that supplies current to the coils 35 and 39, as shown in FIG.
The power supply 4A can output an excitation current and a demagnetization current independently.
This power supply 4A includes an exciting current generator 41 and a demagnetizing current generator 42 as shown in FIG.

In the present embodiment, the excitation current generator 41 is electrically connected to the coil 35 and supplies the excitation current to the coil 35. The degaussing current generator 42 is electrically connected to the coil 39 and supplies a demagnetizing current to the coil 39.
With such a relatively simple configuration, it is possible to realize a power supply 4A that can generate a direct current and an alternating current that decays with time.

The coil 39 constitutes an “alternating magnetic field coil” that is supplied with a demagnetizing current from the power supply 4A and generates an alternating magnetic field component of the demagnetizing magnetic field. The coil 35 constitutes a “DC magnetic field coil” that is supplied with an excitation current from the power supply 4A and generates a DC magnetic field component of a demagnetizing magnetic field. Thereby, a demagnetizing magnetic field can be generated by superimposing an alternating magnetic field component from the coil 39 and a direct magnetic field component from the coil 35.
Thus, by generating a demagnetizing magnetic field using the two coils 35 and 39, the freedom degree of design of 1 A of atomic oscillators can be raised.

Here, since the coil 35 for generating the exciting magnetic field also serves as a DC magnetic field coil for generating the DC magnetic field component of the demagnetizing magnetic field, the number of parts can be reduced, and the atomic oscillator 1A can be reduced in size and cost. .
The magnetic field control unit 73 that controls the power source 4A can switch between a demagnetizing mode that supplies an exciting current to the coil 35 and a demagnetizing current to the coil 39, and a normal mode that supplies the exciting current to the coil 35. It is. Thereby, the 2nd package 36 can be demagnetized at arbitrary timings.

In the demagnetization mode, the magnetic field control unit 73 operates the excitation current generation unit 41 and the demagnetization current generation unit 42 simultaneously. As a result, as shown in FIG. 13, the exciting current and the demagnetizing current are simultaneously output from the power source 4A, and the AC magnetic field component from the coil 39 and the DC magnetic field component from the coil 35 are superimposed to generate a demagnetizing magnetic field. Can be made.
On the other hand, in the normal mode, the magnetic field control unit 73 operates the excitation current generation unit with the demagnetization current generation unit 42 stopped. As a result, only the excitation current is output from the power supply 4A, and the coil 35 is supplied with the excitation current from the power supply 4A to generate an excitation magnetic field.

The coil 39 is disposed between the second package 36 and the package 5 as shown in FIG. Thereby, compared with the case where the coil 39 is arrange | positioned in the 2nd package 36, size reduction of the 2nd package 36 can be achieved. Further, when the second package 36 is an airtight package, the degree of vacuum in the second package 36 can be easily kept high by downsizing. When both the second package 36 and the package 5 have magnetic shielding properties, both the second package 36 and the package 5 can be efficiently demagnetized by the magnetic field from the coil 39.
In the present embodiment, the coil 39 is composed of a solenoid coil disposed concentrically with the coil 35. Thereby, the coil 39 can be disposed by effectively utilizing the space between the second package 36 and the package 5.

The coil 39 can also be formed of a Helmholtz coil that is concentric with the coil 35 and disposed with the second package 36 interposed therebetween.
Also according to the second embodiment as described above, it is possible to prevent or suppress a change in the amount of magnetization of the second package 36 over time due to the magnetic field from the coil 35 and to improve the long-term stability of the frequency.

2. Electronic equipment The atomic oscillator described above can be incorporated into various electronic equipment. Such an electronic device has excellent reliability.
Hereinafter, the electronic apparatus of the present invention will be described.
FIG. 14 is a diagram showing a schematic configuration when the atomic oscillator of the present invention is used in a positioning system using a GPS satellite.
The positioning system 100 shown in FIG. 14 includes a GPS satellite 200, a base station device 300, and a GPS receiver 400.

The GPS satellite 200 transmits positioning information (GPS signal).
The base station device 300 receives the positioning information from the GPS satellite 200 with high accuracy via, for example, an antenna 301 installed at an electronic reference point (GPS continuous observation station), and the reception device 302 receives the positioning information. And a transmission device 304 that transmits positioning information via the antenna 303.

Here, the receiving device 302 is an electronic device provided with the above-described atomic oscillator 1 of the present invention as its reference frequency oscillation source. Such a receiving apparatus 302 has excellent reliability. In addition, the positioning information received by the receiving device 302 is transmitted by the transmitting device 304 in real time.
The GPS receiver 400 includes a satellite receiver 402 that receives positioning information from the GPS satellite 200 via the antenna 401, and a base station receiver 404 that receives positioning information from the base station device 300 via the antenna 403. Prepare.

3. Mobile Object FIG. 15 is a diagram showing an example of a mobile object equipped with the atomic oscillator of the present invention.
In this figure, a moving body 1500 has a vehicle body 1501 and four wheels 1502, and is configured to rotate the wheels 1502 by a power source (engine) (not shown) provided in the vehicle body 1501. In such a moving body 1500, the atomic oscillator 1 is built.
According to such a moving body, excellent reliability can be exhibited.

The electronic device including the atomic oscillator of the present invention is not limited to the above-described ones. For example, a mobile phone, a digital still camera, an ink jet type ejection device (for example, an ink jet printer), a personal computer (mobile personal computer, laptop) Type personal computer), TV, camcorder, video tape recorder, car navigation device, pager, electronic notebook (including communication functions), electronic dictionary, calculator, electronic game device, word processor, workstation, video phone, crime prevention TV Monitors, electronic binoculars, POS terminals, medical devices (for example, electronic thermometers, blood pressure meters, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic devices, electronic endoscopes), fish detectors, various measuring devices, instruments (for example, vehicles) ,aircraft, Instruments of 舶), can be applied to a flight simulator or the like.
The atomic resonance transition device, atomic oscillator, electronic device, and moving body of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.
In addition, the present invention can be replaced with an arbitrary configuration that exhibits the same function as that of the above-described embodiment, and an arbitrary configuration can be added.

Moreover, you may make it this invention combine arbitrary structures of each embodiment mentioned above.
In the above-described embodiment, the case where the light emitting unit and the gas cell are housed in separate packages has been described as an example. However, the light emitting unit, the gas cell, the light detecting unit, and the like are the same package (shielding unit or inner shielding). Part).

In the embodiment described above, the exciting current is used as the direct current for obtaining the direct current magnetic field component of the demagnetizing magnetic field. However, a direct current from a power source different from the exciting current may be used. In this case, it is preferable that the direct current for obtaining the direct current magnetic field component of the demagnetizing magnetic field has the same direction as the excitation current and coincides with or approximates the current value of the excitation current.
In the above-described embodiment, the quantum interference device that resonantly transitions cesium or the like using the quantum interference effect of two types of light having different wavelengths has been described as an example of the atomic resonance transition device of the present invention. The atomic resonance transition apparatus is not limited to this, and can also be applied to a double resonance apparatus that performs resonance transition of rubidium or the like by utilizing a double resonance phenomenon caused by light and microwaves.

DESCRIPTION OF SYMBOLS 1 ... Atomic oscillator 1A ... Atomic oscillator 2 ... 1st unit 3 ... 2nd unit 4 ... Power supply 4A ... Power supply 5 ... Package 6 ... Wiring board 7 ... Control part 21 ... Light emitting part 22 ... 1st package 23 ... Window part 31 ... Gas cell 32 ... Light detection part 33 ... Heater 34 ... Temperature sensor 35 ... Coil 36 ... Second package 37 ... Window part 38 ... Substrate 39 ... Coil 41 ... Excitation current generation part 42 ... Demagnetization current generation part 43 ... Current superposition part 50 ... Body 51 ... Recess 52 ... Support part 53 ... Support part 54 ... Cover 61 ... Through Hole 62 ... Terminal 63 ... Terminal 71 ... Excitation light control unit 72 ... Temperature control unit 73 ... Magnetic field control unit 100 ... Positioning system 200 ... Satellite 221 ... Base 222 ... Lid 22 ··· Terminal 300 ···························································································································· · · · Heating resistor 361 · · · Base 362 · · · Cover 363 · · · Terminal 400 · · · Receiver 401 · · · Antenna 402 · · · Satellite receiver 403 · · · Antenna 404 · · · · · · · · · · · · · · · · · ... Through hole 1500 ... Moving body 1501 ... Car body 1502 ... Wheel a ... Optical axis LL ... Excitation light S ... Internal space S1 ... Internal space

Claims (11)

Metal atoms,
An exciting coil for applying a DC magnetic field to the metal atoms;
A shielding part having magnetic shielding properties;
A power source capable of simultaneously generating a direct current and an alternating current that decays over time;
A degaussing coil for generating a demagnetizing magnetic field in which the direct current and the alternating current are supplied and a direct current magnetic field component and an alternating magnetic field component that decays with time are superimposed;
An atomic resonance transition device comprising: The power source can output a current obtained by superimposing the direct current and the alternating current,
2. The atomic resonance transition device according to claim 1, wherein the demagnetizing coil is supplied with the superimposed current from the power source to generate the demagnetizing magnetic field. A magnetic field control unit for controlling the power source;
3. The atomic resonance transition according to claim 2, wherein the magnetic field control unit can switch between a degaussing mode in which the superimposed current is supplied to the degaussing coil and a normal mode in which the direct current is supplied to the exciting coil. apparatus.   4. The atomic resonance transition device according to claim 1, wherein the exciting coil also serves as the degaussing coil. 5. The power source can output the direct current and the alternating current independently,
The degaussing coil includes an alternating magnetic field coil that generates the alternating magnetic field component when the alternating current is supplied from the power source, and a direct current magnetic field coil that generates the direct magnetic field component when the direct current is supplied from the power source. The atomic resonance transition device according to claim 1. A magnetic field control unit for controlling the power source;
The magnetic field control unit can switch between a demagnetization mode for supplying the DC current to the DC magnetic field coil and supplying the alternating current to the AC magnetic field coil, and a normal mode for supplying the DC current to the excitation coil. The atomic resonance transition apparatus according to claim 5, wherein   The atomic resonance transition device according to claim 5, wherein the excitation coil also serves as the DC magnetic field coil. The shielding part includes an inner shielding part and an outer shielding part arranged inside and outside,
The DC magnetic field coil is disposed between the metal atom and the inner shielding portion,
The atomic resonance transition device according to claim 5, wherein the alternating-current magnetic field coil is disposed between the inner shielding portion and the outer shielding portion.   An atomic oscillator comprising the atomic resonance transition device according to any one of claims 1 to 8.   An electronic apparatus comprising the atomic resonance transition device according to claim 1.   A moving body comprising the atomic resonance transition device according to claim 1.

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